#!usr/bin/env python  
# -*- coding:utf-8 -*-
""" 
@author:robot
@file: stair.py 
@version:
@time: 2024/01/16 
"""


def stair(n):
    if n == 1 or n == 0:
        return 1
    else:
        return stair(n - 1) + stair(n - 2)


print(stair(4))
